Hang out at /r/fitness, and tons of references will be thrown at you over time with even more advocating one or another nuance. The results in progress/achievement posts quite consistently emphasize that if you don't pay attention to the diet, you'll quickly wreck any gains you sweat out in your workouts. People are only too happy to cite research papers in discussions when asked, but I have yet to see a study so overwhelmingly conclusive that even the food, medical, pharma and exercise industries will concede the point.